Juniper Networks Junos OS ACX Series Forwarding Engine Board Denial-of-Service Vulnerability

A denial-of-service vulnerability has been identified in Juniper Networks Junos OS running on specific end-of-life ACX Series platforms. When 'hot-standby' mode is configured for an L2 circuit, flapping the primary path port can cause the Forwarding Engine Board (FEB) to crash, disrupting service. This issue affects all versions of Junos OS prior to 21.2R3-S9 on ACX1000, ACX1100, ACX2000, ACX2100, ACX2200, ACX4000, ACX5048, and ACX5096 devices.

Impact

Exploiting this vulnerability causes the Forwarding Engine Board to crash, leading to a denial-of-service condition on the affected device.

Reproduction

The vulnerability can be reproduced by configuring an L2 circuit to 'hot-standby' mode on an affected ACX Series device. Once this configuration is in place, flapping the primary path port of the L2 circuit will cause FEB0 to crash. This issue was observed during normal production usage.

Remediation

Users can upgrade to Junos OS version 21.2R3-S9 to address this vulnerability. Note that support for the ACX2k Series ended with Junos OS 21.2.